Convert strconcat*() from galloc() to malloc()
Check for bad info before going further in processing bezctx info
Test for problems in SpiroCP2SplineSet(), if yes, cleanup and exit.
Less math in SpiroCPCopy()
SpiroCPCopy() can copy open or closed spiros now - and don't modify 'n'
Remove repeated code in 2 functions for splineutil.c
prep SplinePointCreate() for possible error if (future) chunkalloc fails
Make SSRegenerateFromSpiros() more robust against problem spiros

Before discarding prior splineset, create new data, then release old data.
Merge pull request #787 from JoesCat/master

libspiro improvements to prevent crashes and segfaults